In agriculture, devices are known in the shape of either smooth or toothed disc. By rotating due to land contact, such discs are able to dig groove on the land, to execute operations like ploughing, seeding, fertilizer spreading and other similar operations.
Usually, such discs are assembled side by side to correspondent shafts, which embossed protrude from the frame of an agricultural machine. Each disc is rotatable assembled, by means of a hub-bearing assembly, which comprises one or two radially inner rings, stationary, the inner rings steadily fixed to a central shaft, which embossed protrudes from an arm of the frame of an agricultural machine, a radially outer ring and a double row of balls, which is interposed between the outer ring and the inner rings. The inner rings, and consequently the bearing, are axially locked against the shoulder of the shaft, due to the tightening of a sleeve or a nut, which is screwed at a free end of the shaft. The outer ring can be contained in a housing, which is in one piece with an external radial flange, for assembling the disc. The housing is covered by a closing cap, which can be press-fit into the housing or screwed on it.
Document EP 1 477 329 A1 discloses a hubcap for a wheel hub. The hub is threaded and preferably includes several notches in its otherwise smooth radially outer end face. The hubcap has an open end terminating in a threaded end portion, a closed end and a discontinuous radial flange (72) between the ends. One or more latching tabs fit into the discontinuities in the flange, and each tab contains a projection which fits into the notch. The tab can be manually lifted to disengage the tab from the notch, but the hubcap cannot otherwise be unscrewed.
Of course, the assembly of the closing cap on the housing requires either a dedicated tooling for press-fit operations or, in case of screwed cap, suitable threads, namely an external thread for the housing and an internal thread for the closing cap. Independent on the chosen solution, additional machines and longer working time are required, thus leading to a long, difficult and expensive process. Moreover, considering the working environment, known solutions do not allow an easy disassembling of the cap.